Vending machines, game machines and the like are provided with a device for detecting the presence of coins (including not only coins used as money but also coin-type tokens for game machines, etc.). This device is used for example to detect the existence of coins in a cylinder for storing change in a coin processor of a vending machine, and the detection by the device is made by various methods.
The method of detecting a coin includes an optical method as disclosed in the U.S. Pat. No. 4,413,718. This method uses a light emitting device and a photodetector which are mounted in the neighborhood of a coin-storing cylinder and detects that light is blocked by the coins stored in the cylinder.
Another method detects the existence of a coin by a proximity switch which has a coil as disclosed in the U.S. Pat. No. 4,460,003.
Now, detection of the presence of change by a coil in the coin processor used for the vending machine or the like will be described.
FIG. 12 is front diagram schematically showing coin processor.
In FIG. 12, a coin processor 560 has a coin insertion port 561 for receiving a coin 531, coin passages 562 (562a to 562d) for rolling and transporting the coin 531 inserted from the coin insertion port 561, a coin inspection unit 563 located near the coin passage 562a for judging whether the coin passing through the coin passage 562a is real or not and its money type, a dividing unit 564 for guiding a counterfeit coin from a counterfeit coin passage (not shown) to a return port (not shown) based on the judgement made by the coin inspection unit 563 and guiding a true coin to one of the coin passages 562b to 562d according to its money type, and a coin storing unit 530 for storing coins according to their money types.
The coin storing unit 530 comprises three cylinders 530a to 530c so that a maximum of three types of coins can be stored. The cylinders 530a to 530c are provided with coils 501a to 501c respectively.
FIG. 13 is a cross sectional view taken along line A-A' of the coin processor 560 shown in FIG. 12.
As shown in FIG. 13, the coils 501a to 501c are arranged in the neighborhood of the cylinders 530a to 530c respectively to detect the presence of coins in the cylinders when the number of coins is at least a predetermined number.
FIG. 14 is a diagram showing a circuit structure for detecting the presence of coins by means of the coils 501a to 501c.
The coil 501a (L51) is connected with an oscillation unit 504a as shown in FIG. 14 and then with a comparison judgment circuit 507a and a reference value circuit 508a via the oscillation unit 504a. In the same manner, the coil 501b (L52) is connected with an oscillation unit 504b and then with a comparison judgment circuit 507b and a reference value circuit 508b via the oscillation unit 504b. Coil 501c (L53) is connected with an oscillation unit 504c and then with a comparison judgment circuit 507c and a reference value circuit 508c via the oscillation unit 504c.
In the configuration described above, the coil 501a (501b, 501c) is excited at a fixed frequency by the operation of the oscillation unit 504a (504b, 504c). When a coin approaches the coil 501a (501b, 501c), an inductance L1 (L2, L3) of the coil changes (including changes of impedance (R+j.omega.L) and Q(.omega.L/R)), resulting in varying an oscillation frequency. The comparison judgment circuit 507a (507b, 507c) compares the oscillation frequency with a reference value generated by the reference value circuit 508a (508b, 508c) to detect the presence 510a (510b, 510c) of the coin.
Of the above-mentioned conventional technologies, the optical type can be configured relatively easily but has a drawback that, for example, dust or the like adheres to cause malfunction.
Meanwhile, the one using a coil is extensively used because it is resistant against dust or the like. But, an inspection circuit which contains the oscillation circuit and the like is needed for each coil and becomes complex. Besides, it is necessary to differentiate the oscillation frequency of each circuit to avoid the interference between the coils. It is also necessary to make the temperature compensation of the inspection circuits individually because the oscillation frequency is different in each inspection circuit.
Thus, in the conventional technology using the coil, two or more inspection circuits are necessary and such circuits must be adjusted individually. Therefore, the circuits become complex, and the number of parts increases. And the manufacture and adjustment of the circuits become complex and expensive.